Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

After massive experiment, results favor wildlife corridors

17.09.2002


To combat urban sprawl and protect wildlife, many communities have set aside land for wildlife corridors linking natural areas to one another.



Public support for these greenways, however, has overshadowed a long-running debate among ecologists about whether they actually achieve their presumed benefits. The debate has been hobbled by a lack of definitive data, with many studies based solely on observations and others only on small-scale experiments, scientists say.

A University of Florida-led study may help resolve the issue. Set to appear next week in the Proceedings of the National Academy of Sciences, the study examines two barometers of healthy ecosystems – plant pollination by insects and the dispersal of seeds by birds – and concludes that corridors encourage the movement of plants and animals across "fragmented" landscape. The findings of the study are important, its authors say, because it is based on a much larger and more ambitious experiment than typically attempted.


"This is by far the largest experimental look at the effects of corridors that has ever been done," said Josh Tewksbury, a UF postdoctoral associate and the study’s lead author.

Intuitively, wildlife corridors make sense. First envisioned as early as the 1960s, they are seen as ways to allow wildlife and plants to spread across natural landscapes that have been cut into pieces by roads, development, logging or other disturbances. The idea is that corridors not only allow animals to find new resources, they also prevent the isolation of species – isolation that can lead to localized extinction if the habitat fragments are not accessible for reproduction or recolonization. Finding support for this seemingly simple theory, however, is more difficult than might appear, said Doug Levey, a UF professor of zoology and one of the study’s authors.

Previous studies have shown that wild areas connected by corridors have more wildlife or greater biodiversity than disconnected areas. But these studies often failed to account for other factors that may have influenced the observed differences, Levey said. For example, corridors in urban areas often lie along streams or rivers because these flood-prone areas tend to be left undeveloped. But waterways represent one type of habitat that may benefit wildlife and plants more than the corridors themselves, he said. If that’s the case, it would be better to preserve such habitats wherever they are rather than only those that connect fragments, he said.

Experiments on corridors, meanwhile, are difficult to pull off because the areas needed to test and repeat them are so large – at least for large animals that typically range over wide areas.

An experiment exploring whether corridors benefit black bears, for example, would require an area equal to the bears’ range of hundreds of miles. And other similarly huge natural areas would be needed to repeat the experiment to test its conclusions. As a result, most scientifically rigorous corridor experiments have taken place on much smaller scales. One noted experiment, for instance, focused on insect distribution on 20-by-20-square-inch plots of moss arranged in connected and unconnected patches.

The UF-led team sought to increase the scale considerably.

The researchers mapped out eight similar sites, each about 158 acres along the South Carolina-Georgia state line. This site, the Savannah River Site National Environmental Research Park, is a 482-square-mile federally protected research area originally set aside during the Cold War for nuclear weapons development.

Forests of 50-year-old pine trees dominate all eight sites. At the researchers’ request, the U.S. Forest Service arranged for workers to log trees and burn the remaining groundcover in selected areas, creating one central clearing and four peripheral clearings on each site. They also logged corridors connecting each central clearing to one of the peripheral clearings, leaving the others separated by the forests. Each the clearing measured about two acres.

With 40 total clearings, the scale of the experiment can best be appreciated from the air. As seen from a plane flying at several thousand feet, each one of the eight sites looks more like a large crop circle or alien launch pad than a biology experiment. From a satellite, the arrangement of eight total sites is even more impressive.

Created in 1999, the clearings quickly grew into fields. These habitat "patches" provided what Levey called "black and white" habitat types when compared with the forest – plants and animals found in the fields would never flourish in the forest and vice versa. Research on the sites lasted for two years, with most data collected in 2000 and 2001.

For one of two major experiments, the researchers planted male holly bushes in the central patch and female hollies in the four peripheral patches. They chose holly because it is not naturally present in the forest and the female trees cannot bear fruit unless pollinated by males. The researchers waited until the hollies had flowered and then measured the fruit set, or the percentage of flowers that turned into berries, in each of the clearings.

The result: The hollies in the connected patches were consistently more fruitful than in the unconnected ones. This indicated that more wasps, butterflies and other insect pollinators made it from each central patch through the corridor than through the forest.

When birds or other animals eat fruits, they often distribute the seeds to new locations in their droppings, an important mechanism of plant dispersal. To gauge the effects the corridors had on this process, the researchers marked thousands of seeds of wax myrtle and holly in the central patch with a sticky powder that can be seen only with a florescent light. The researchers then placed seed traps under 16 bird perches built in each of the connected and unconnected peripheral patches. Over several months, they collected and analyzed the resulting bird droppings in a lab.

Given the grand scale of the experiment, the work was not without difficulties. "We collected thousands and thousands of defecations from birds, and it takes a lot of time to go through them all," Tewksbury said. The resulting data revealed that significantly more droppings containing wax myrtle and holly seeds were carried from the central patches to the connected patches than to the unconnected patches. This indicated that more birds were flying between the connected patches than the unconnected ones. "There was almost double the (center patch’s) droppings in the connected receiver patches versus the unconnected patches," Levey said.

The findings may go well beyond pollination and seed dispersal. When plants have more pollen, they produce more fruit, attracting more birds, which distribute more seeds, which attract more birds and seed-eating animals, and so on. So although the experiment tested only two processes, it suggests that corridors can be beneficial in the much larger biological community.

"Our study suggests that these corridors do help in connecting populations, and theoretically they should help sustain networks of populations existing in increasingly fragmented landscapes," Tewksbury said.

The research team also included zoologists Nick Haddad, of North Carolina State University, Brent Danielson of Iowa State University, Sarah Sargent of Allegheny College in Pennsylvania and numerous graduate students.

Josh Tewksbury | EurekAlert!
Further information:
http://www.ufl.edu/

More articles from Ecology, The Environment and Conservation:

nachricht How fires are changing the tundra’s face
12.12.2017 | Gesellschaft für Ökologie e.V.

nachricht Using drones to estimate crop damage by wild boars
12.12.2017 | Gesellschaft für Ökologie e.V.

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Long-lived storage of a photonic qubit for worldwide teleportation

MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.

Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...

Im Focus: Electromagnetic water cloak eliminates drag and wake

Detailed calculations show water cloaks are feasible with today's technology

Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...

Im Focus: Scientists channel graphene to understand filtration and ion transport into cells

Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.

To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...

Im Focus: Towards data storage at the single molecule level

The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.

Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...

Im Focus: Successful Mechanical Testing of Nanowires

With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong

Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

AKL’18: The opportunities and challenges of digitalization in the laser industry

07.12.2017 | Event News

 
Latest News

A whole-body approach to understanding chemosensory cells

13.12.2017 | Health and Medicine

Water without windows: Capturing water vapor inside an electron microscope

13.12.2017 | Physics and Astronomy

Cellular Self-Digestion Process Triggers Autoimmune Disease

13.12.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>